The difference between classical music and rock, is that classical composers actually knew what to say and how to say it. Rock is a frustrated and nervous thing, where people only stumble on brilliant speech. It’s not that it is not great, but that it is usually great by accident or chance stumbling on figures that our fathers had already thoroughly explored. So, the greatness of rock is explanation and innovation, but the success of this freedom is judged by their discovery of order.
The pursuit of classical music is control through skill and order. The pursuit of rock is the expulsion of all rules and order. Which is ironic, because the greatest pieces of rock are highly ordered and full of skill.
Progressive rock and song cycles are the spiritual successors to Handel’s Messiah and classical pieces. And the reasons they succeed are for largely the same reasons. If only the “artist” knew they are great, not because of their genius, but because they are just a part of the whole ordered universe. The only pieces in front of them to use for success and moving emotion are order and skill. This is why music really can objectively fail or succeed. You might be able to break rules, but you will fail to persuade.
Sometimes, rock succeeds in persuasion more than classical music ever could, because of the tools in front of it. There is precision and sensation in more great abundance, potentially. If only we knew what we were doing.